Last year at DS my wife almost went ballistic on a security guy that was rudely barking orders at her like she was under arrest because her sunglasses case (we think) triggered the scanner. We were going through with a bunch of other people (strangers) and it wasn't clear at all who they were trying to get the attention of.
She was addressed in a manner that was like she was trying to escape from prison and she'd be shot if she didn't comply with his instructions. During the whole secondary screening she was as rude as she could possibly be right back to him to make a point.
She was wearing a tight fitting t-shirt and shorts and had her cell phone in her pocket (protruding and making an outline) and she was holding the small sunglasses case. Even with the scanner alerting, there is no way she could have been concealing anything other than maybe a very small switchblade that would fit in the sunglasses case. Common sense would dictate that, based on these facts, it was most likely a false alert and she should have been asked in a friendly and apologetic manner to stop for a screening. She shouldn't have had orders rudely screamed at her.